Hint: You can stop your search at sqrt(n). In the present case, sqrt(1248)=35.327... Therefore check natural numbers to 35.

Method2 (easy):

Use mod key on calculator.

Ex 2: List factors of 330.

Solution:

Enter 330 into memory (330 STO).

Sqrt(330) = 18.17... Therefore check up to 18.

On calculator, systematically enter (MR)mod(k) for all k in {1, 2, 3, ..., 18} (MR <=> MEM-RECALL). You can isolate factors by utilizing the fact that k is a factor of n iff n_mod(k)=0. For example, 330mod(8) = 2. Thus 8 is not a factor of 330. 330mod(15)=0. Thus 15 is a factor, as is 22 (330/15=22).